ACQUISITION. 80. Not only may Discrimination and Instinct be manifested in the absence of the brain, but even the acquisition of new modes of reaction, such as are classed under Learning through Experience. The objection is sometimes urged that animals without their brains only manifest single reactions on stimulation- the pinched foot is withdrawn, and then remains motionless until again pinched. But although the stimulation does not excite a consecutive series of movements, because there is no cerebrum to react in successive stimulation, this does not prove the absence of sensation in the one movement which is excited. If my hand be lying on the table, and something irritates it, my hand is withdrawn, and then remains as motionless as the limb of the brainless animal, until some fresh stimulation, external or internal, moves it. Although removal of the brain causes a manifest reduction in the variety and succession of the movements, all experimenters are agreed that animals acquire a certain dexterity in executing actions which they had previously failed to carry out after removal of their brains. "There is," says Freusberg, "a decided improvement acquired in the reactions of the motor centres after division of the spinal cord, not indeed in vigor, but in delicacy. Removed from the regulating influence of the brain, the legs acquired through practice a power of self-regulation." Nor is this wonderful: pathways are made easy by repetition of impulses, and new adaptations form new adjustments. It is thus all learning is effected-intelligent, and automatic. Nor is there any force in the objection. that the power thus acquired speedily disappears, so that if the stimulations are effected at long intervals the reactions do not manifest their acquired dexterity. The spinal centres forget, as the cerebral centres forget; but they also remember, i. e. they learn. Because an animal shows today none of the aptitude it acquired three days ago, we are not to deny that it had once acquired the aptitude it has now lost. Attempt to teach a child to read by giving it spelling lessons of two or three minutes at intervals of two or three months, and little will the acquisition be! 81. Hitherto we have been considering phenomena manifested in the absence of the cerebral hemispheres, because it is in these that the majority of writers place the sensorium. There are, indeed, many authoritative writers who regard the ganglionic masses at the base of the cerebrum, and even those of the medulla oblongata, as participating in this sensorial property, which they refuse to the lower ganglia in the spinal cord. I cannot follow their logic. The cerebrum is by its position as a centre of centres, and its detachment from all direct innervation of organs, so different from the rest of the neural axis, that we can understand how it should be assigned a special function; although being of the same tissue as the other ganglionic masses, it must have the same property. And what that special function is I shall hereafter endeavor to set forth. But that the upper region of the spinal axis should differ so profoundly from the lower region as to be the seat of psychical processes, while the lower region is simply the seat of mechanical processes, is what I cannot understand, so long as the anatomical structure and physiological properties of the two regions are seen to be identical. The various centres innervate various organs, and have consequently various functions. As each centre is removed, we observe a corresponding loss of function-the organism is truncated, but continues to manifest such functions as have still their mechanisms intact. Let us suppose the brain or upper regions of the cord detached from the lower regions by a section of the cord; the animal will still live, and perform almost all its functions in the normal way, but there will be little or no consensus between the lower and the upper regions. Granting Sensibility to both, we must still see that the sensation excited in one will not be felt in the other. And this is the ground on which physiologists deny that the lower regions have Sensibility. Without pausing here to examine this point, which will occupy us in the next chapter, I assume that the positive evidence of Sensibility suffices to discredit that argument; and in furtherance of that assumption will cite an example of sensation and volition manifested by the lower portion of the cord when separated from the brain and upper portion. 82. The function of Urination is one which notoriously belongs to the voluntary class, in so far as it is initiated or arrested by a voluntary impulse, and it is one which, according to the classic teaching, has its centre in the brain. The grounds on which this cerebral centre is assigned are very similar to those on which other functions are assigned to cerebral centres, namely, observation of the suppression of the function when the pathway between certain organs and the brain is interrupted. But the careful experiments of Goltz* have demonstrated that the "centre" of Urination is not in the brain, but in the lower region of the cord. When the cord is completely divided, Urination is performed in the normal way not passively, not irregularly, but with all the characters of the active regular function. And, what is also noticeable, this function is so intimately dependent on Sensibility that it will be arrested-like any other function by a sensation excited from the peripheryto be resumed when the irritation ceases. Now this *Pflüger's Archiv, Bde. VIII. and IX. arrest from a stimulation of sensory nerves takes place when the brain is cut off from the spinal centre, just as when the brain is in connection with it. The same is true of Defecation, and the still more complex functions of Generation and Parturition. only refer the reader to the very remarkable case of Goltz's bitch with the spinal cord divided in the lumbar region, if evidence be wanted for the performance of complex functions so long as the spinal centres were intact. It is true that Goltz considers these functions to have been independent of sensation; but that is because he has not entirely emancipated himself from the traditional views; for my purpose it is enough that he admits the functions to be dependent on sensorial processes. 83. To sum up the evidence, we may say that observation discloses a surprising resemblance in the manifestations of the cord and brain. In both there are reflex processes, and processes of arrest; in both there are actions. referable to conscious and unconscious processes; in both depression and exaltation are produced by the same drugs; in both there are manifestations interpretable, as those of Discrimination, Logic, Instinct, Volition, Acquisition, Memory; in both there is manifestation of Sensibilityhow then can we deny Sensation to the one if we accord it to the other? CHAPTER IV. NEGATIVE INDUCTIONS. 84. I FANCY Some reader exclaiming: "All your reasoning, and all your marshalled facts, are swept away by the irresistible evidence of human patients with injured spinal cords, whose legs have manifested reflex actions, and who nevertheless declared they had no sensation whatever in them. We can never be sure of what passes in an animal; but man can tell us whether he feels an impression, or does not feel it; and since he tells us that he does not feel it, cannot, however he may try, we conclude that reflex action may take place without sensation." As this is the one solitary fact which is held to negative the mass of evidence, anatomical and physiological, in favor of the Sensibility of the spinal cord, it is necessary that we should candidly examine it. No reader will suppose that during the twenty years in which I have advocated the doctrine expounded in this volume, I have not been fully alive to the one fact which prevented the general acceptance of the doctrine. From the first it has seemed to me that the fact has been misinterpreted. 85. Certain injuries to the spinal cord destroy the connection of the parts below the injury with the parts above it; consequently no impression made on the limbs below the injured spot is transmitted to the brain, nor can any cerebral incitation reach those limbs. The patient has lost all consciousness of thesc limbs, and all |